1. Field of the Invention
The present invention relates to a belt conveying apparatus for use in an image forming apparatus such as an electrophotographic copying machine and an image forming apparatus.
2. Description of the Related Art
A fixing device of a belt fixing system (i.e., an endless belt conveying apparatus or an image heating device) has been conventionally used in an image forming apparatus (Japanese Patent Application Laid-Open No. 2004-341346). In a fixing device of a belt nip system using a so-called endless belt for a fixing belt or a pressurizing belt, there has arisen a problem of a fatigue breakage due to repeated bending of a belt or a breakage of a belt due to the abutment of a belt end against a deviation preventing/restricting member for a belt. Moreover, there has also arisen a problem of speedy detection of a brakeage with certainty so as to stop an apparatus when a belt is broken.
In view of the above, a configuration, described below, has been proposed in order to speedily detect the breakage of a belt so as to properly take measures to the breakage (Japanese Patent Application Laid-Open No. 2002-287542). That is to say, there has been proposed a method for marking a belt so as to detect a breakage according to a change in marking cycle by a sensor. Alternatively, there has been proposed a method for allowing a contact piece to abut against a belt, and further, detecting non-abutment of the contact piece by a sensor, so as to detect a breakage on the belt.
However, in the belt conveying apparatus or the image heating device, the belt is liable to be broken at the end thereof caused by the configuration of the apparatus, a belt fabricating method, or the like. As a consequence, in the case where the sensor or the contact piece for detecting the breakage of the belt is disposed, as disclosed in Japanese Patent. Application Laid-Open No. 2002-287542, it is necessary to dispose the sensors or the contact pieces at both ends of the belt, thereby inducing complication and cost-up.